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In this study, the lattice Boltzmann method was used to simulate the three-dimensional intrusion process of liquid water in the gas diffusion layer (GDL) of a polymer electrolyte membrane fuel cell (PEMFC). The GDL was reconstructed by the stochastic method and used to investigate fiber orientation's influence on liquid water transport in the GDL of a PEMFC. The fiber orientation can be described by the angle between a single fiber and the in-plane direction; three different samples were simulated for three different fiber orientation ranges. The simulated permeability correlated well with the anisotropic characteristics of reconstructed carbon papers. It was concluded that the fiber orientation had a significant effect on the liquid invasion pattern in the GDL by changing the pore shape and distribution of the GDL. The results indicated that the stochastically reconstructed GDL, taking into account the fiber orientation, better demonstrates the mass transport properties of the GDL.

Storage of liquefied gas in an underground cavity created in hard rocks is a promising new technology that can significantly reduce the dimensions of a storage facility. The intense heat transfer between the cryogenic fluid and the surrounding rocks leads to the formation of an ice ring in water-saturated rocks, which acts as a natural protective barrier. In this paper, we provide a general theoretical analysis of the existence and evolution of the freezing ring. The analysis is based on solving the problem of heat transport in heterogeneous domain with two thermal waves initiated inside the domain and propagating into two opposite directions. The analytical solution was obtained by the modified Karman–Pohlhausen integral method. We have developed the extension of this method to a heterogeneous medium, in which the effect of the temperature semi-stabilization occurs. It has been shown that the propagation of the freezing front is non-monotonic and changes direction, so that the lifetime of the ice ring is finite. General analytical formulae have been obtained that describe all process parameters depending on the thickness of the insulating layer, in particular: the maximum thickness of the ice ring, its lifetime, conditions of existence, the critical thickness of the insulation above which the ice ring does not arise, as well as the global evolution of the temperature field. These results enable to select an optimal thickness of the insulation.

The accidental releases of pressurized liquefied gases from tanks involve violent phase transformation, which would generate two-phase releases and flashing jets. To investigate the evolution of leakage behaviors and make an analysis of near-field jet flow characteristics, a small-scale liquefied gas release experiment has been established. Leakage holes with different length-diameter ratio (LDR) have been used to analyze interactions between the leakage holes and release behaviors. Morphological characteristics of jet expansion angles have been obtained by high-speed camera, and jet velocities have been measured by particle image velocimetry (PIV). Meanwhile, the depressurization process, variation of temperature in the tank and mass outflow rates were obtained. Results show that, despite the LDR is varying, expansion angles and jet velocities behavior in the same tendency: decreases in the initial and maintains in a stable value for a period. The stable velocity status was worked by the balanced pressure drop. Thereafter, an empirical two-phase mass outflow rate model is developed based on the experimental data, which is related to the nozzle geometric parameter and upstream pressure, 90 % of the experimental data are within ±12 % of the prediction. Therefore, the empirical two-phase model can be supported in the mass flow rate evaluation, especially for the release cases that LDR are smaller than 5.00 but larger than 2.00. The experimental data is beneficial for providing further insight into the prediction of accidental release and risk assessment for the liquefied gas transportation and storage.

The gas suction rate of a conventional liquid–gas ejector pump was measured on a modular pilot plant unit utilizing convergent nozzles and a water–air system. Hydraulic characteristics were measured for various water flow rates, suction and discharge pressures, and ejector geometries, covering a wide range of configurations and operating conditions. The device configurations, providing the most stable and reproducible results, were identified. The air flow rates measured with these configurations were correlated by a simple, three-parameter correlation with a relative standard deviation (RSD) of 11%. The performance and behavior of the ejector in less stable configurations are discussed and the recommendations for the design of optimally operating units are provided. Finally, the correlation is tested against available literature data. The ejectors with comparable geometry agree well with the proposed correlation (within 20% RSD). The reasonable agreement with the discussed differences is found for other literature data. This comparison results in the validation of the proposed correlation to provide a safe prediction of minimal gas entrainment in units of various geometries, orientation and operating conditions.

The theoretical model of main performance indicators of diesel locomotive engines using natural gas is exposed. According to the model, the heat released during the combustion of mixed fuel can be determined. The composition of natural gas, which is indicated in the passport when refueling a diesel locomotive, is taken into account. Thus, it became possible to adjust the program of regulating the fuel supply control system according to the operating modes of a diesel locomotive engine by introducing a composition coefficient. The results of analyzing the variation range in the net calorific value of gas during the conversion of diesel locomotives for using the natural gas as a motor fuel are presented. As exposed, the variation range in the net calorific value at various examined fields varies up to 32.4%. The so-called net calorific value of diesel fuel and natural gas combustion is suggested to be considered for operating diesel locomotive engines with liquid gas fuel, in addition to atmospheric conditions.

International audience; The boiling liquid expanding vapour explosion (BLEVE) is well known but not well understood. Some still argue about what comes first, the BLEVE or the vessel rupture. Some believe the BLEVE is triggered by some pressure transient inside the vessel and this causes a superheat limit explosion which causes the vessel to rupture. Others believe it is the vessel rupture by some weakening process that leads to the BLEVE. This paper will provide evidence that the latter description that is correct for most, if not all BLEVEs observed in practice. This paper describes small scale experiments of aluminum tubes that were weakened by machining a thinned wall area over a specified length. The tubes were filled to a desired level with liquid propane and then the propane was uniformly heated electrically until the tubes failed. The failure pressures ranged from 10 to 33 bar. The tube was instrumented to capture failure characteristics (pressure, temperature) and consequences: blast overpressure and imaging of the propane cloud and shock around the vessel; ground force under it; transient pressure and imaging of the boiling process inside the vessel. The work was done to improve our understanding of the fluid – structure interactions during the fire heat induced failure of a pressure vessel holding a pressure liquefied gas. We were specifically interested in the near field hazards including blast overpressure and ground force. This paper will focus on the early milliseconds of the process where the vessel begins to open and a shock wave is formed and moves out into the surroundings. The imaging reveals presence of a Mach shock at the exit of the vessel at the early stage of the opening. A chronology of the event also shows that the lead shock is generated early in the explosion process, and is long gone before the liquid starts boiling, arguing that vapour expansion is the main contributor to the first shock overpressure.

Natural gas liquefaction cycles require high amounts of shaft power and any effort for decreasing power consumption of these cycles is a subject of interest. Among natural gas liquefaction cycles, N 2 and N 2 /CH4 cycles with CO2 pre-cooling are attractive due to their simplicity. The novel work here is that two above cycles are first modified. Then by choosing the ratio of power consumption to the liquefied gas molar flow rate (Specific Energy Consumption, SEC) as the objective function and 13 design parameters for N 2 -CO 2 cycle and 12 design parameters for N 2 /CH 4 -CO 2 cycle, these cycles are optimized. Results of the above procedure showed decrease in both SEC and the total annual cost in comparison with those for similar cycles published in open literature. Two modified and optimized N 2 -CO 2 and N 2 /CH 4 -CO 2 liquefaction cycles showed 5.25% and 3.62% decrease in specific energy consumption and 9.4% and 16% decrease in exergy destruction respectively. The total cost of two above cycles also decreased for 0.5% and 1.2% respectively.

Developing design tools to make more information available sooner is desirable because decisions of the greatest impact are made in early stages of ship design. Moreover, there is still room for improvement in the optimisation of energy system selection considering an integrated approach. Therefore, the present work aims to provide a comprehensive early-stage approach to optimise the design, synthesis and operation of a marine energy system for liquified gas carriers, considering their economic and technical aspects, and also weather along the route. Constraints are used to avoid propellers that could present issues concerning strength, cavitation and vibration. Various propellers, engines and operational profiles can be assessed with this approach. A differential evolution optimisation algorithm that maximises the net present value is applied. This part of the study details the approach that we have developed, while the case study, results and discussion, and the main conclusions are given in Part B. Different parameters can be set up in each route-track, which enables various operational profiles and sea conditions to be considered to seek the highest net present value. The proposed approach is expected to be able to automatically search a broad range of possible alternatives and then make small refinements to achieve the optimal arrangement.

Downward gas-liquid slug flow occurs in hilly-terrain pipelines and is frequently observed in oil and gas transportation lines. The onset of this kind of flow owes to instabilities generated by irregular pipe topography. Therefore, a solid understanding on the hydrodynamics of the slug flow is paramount in the design of crude oil production lines as well as in the project of equipment involved in oil and gas operations. The goal of this work is to analyze the mean values of the translational velocity, slug frequency, bubble and slug lengths in ducts with inclination angles from −4° down to −13° on experimental grounds. The analyses were performed at different gas-liquid volumetric flow rates for which the slug flow regime was observed. An existing experimental rig in the NUEM/UTFPR labs was used to collect data. A pair of wire-mesh sensors was used to evaluate the flow structure, and thence void fraction temporal series were obtained. From those temporal series, the experimental data were obtained and comparative analyses could then be made. The mean bubble (C0) and drifty velocity (C∞) coefficients were determined for the translational velocity. The mean bubble and slug lengths were compared for minimum and maximum values. A schematic of the unit cell behavior in downward slug flow is proposed.

Two kinds of usage environments need to be considered for development of hydrazine sensor: the detection of hydrazine in liquid phase and the detection of hydrazine gas in air environment. Here, Au nanoparticles-embedded N-doped porous carbon anchored on reduced graphene oxide (AuNPs@NPC-rGO) nanosheet has been creatively constructed by a confinement preparation process in the frame structure of zeolitic imidazolate framework-67 (ZIF-67). Such ternary hybrid material exhibits good sensitivity for the detection of harmful hydrazine in liquid/gas phase. First, an electrochemical sensor based on AuNPs@NPC-rGO modified glassy carbon electrode (AuNPs@NPC-rGO/GCE) has been established for detection of hydrazine in liquid phase, leading to the linear detection range from 0.05 to 1.00 μM and the detection limit of 9.6 nM. Second, a practical electrochemical gas sensor based on AuNPs@NPC-rGO has been assembled for the detection of hydrazine gas in air environment. Such gas sensor shows the detection limit of 1.8 ppm with fast response/recovery. Those advantages of the electrochemical sensors based on AuNPs@NPC-rGO can be attributed to the key design element of sensing material with structural and compositional advantages leading to the synergy of AuNPs, NPC and rGO.

The boiling liquid expanding vapor explosion (BLEVE) is a most severe hazard in liquefied gas storage and transportation, and its prevention depends on the suppression of the explosive boiling during tank depressurization. This paper proposes an idea of using micro-fin type surface to suppress the explosive boiling, and experimentally investigates the suppression mechanisms and quantitative effects on the explosive boiling. In the experiments, the bubble behaviors on a micro-fin and a smooth surface are observed for phenomenal analysis, and the explosive boiling consequences of the two surfaces are measured for quantitative evaluation. The results show that, the micro-fin surface brings forward the nucleation onset and reduces the boiling region, resulting in a weakened explosive boiling process. Among release pressures of 200 kPa-500 kPa and vent areas of 1.8 cm2-5.3 cm2, the adopted micro-fin surface reduces the boiling-induced pressure rise and the released energy by up to 24.5% and 35.6%, respectively.

liquid–gas interface (LGI) on submerged solid structured surfaces is ubiquitous in nature and has various practical applications. The evolution, equilibrium, and stability of LGI are crucial to the underwater performances and functionalities of the surfaces, such as wetting, drag reduction, heat and mass transfer, etc., and have been studied for decades. In this review, we systematically summarize the underlying mechanisms of the morphology evolution of LGI on submerged solid structured surfaces under both quiescent and flow conditions. First, a thermodynamic framework for the analysis of the equilibrium and stability of submerged LGI in quiescent ambient is introduced. The conditions necessary to achieve equilibrium are surveyed. Then, both effects of hydrostatic pressure and gas diffusion on the morphology evolution of submerged LGI are reviewed. Some specific topics on interface morphologies, critical pressure, metastable state and gas diffusion equilibrium state are discussed. Finally, the morphology evolution of LGI under flow conditions is reviewed, including the effects of laminar and turbulent shear flow, and the flow enhanced gas diffusion.

Energy use optimization is one of the numerous way to reduce the impact of the CO2 on the environment. The work presented in this paper explores the possibility to apply the Brazed Plate Heat Exchanger (BPHE) technology to enhance the heat transfer between an extremely cold liquid gas such as nitrogen or air and low-grade heat media such as hot water. BPHEs are known to be characterised by high turbulent flows and high heat transfer rate and thus are the best candidate to guarantee quick heat transfer between the two fluids. Particular concern in this application is given by the risk of freezing water inside the BPHE. Considering the high complexity in the internal structure of the BPHE, the work is based on its analysis using x-ray tomography and CFD via a commercial software. CFD analysis was carried out using a first simple geometry and physics to verify the feasibility of the study. Given the promising results (quick heat transfer and tempered water temperature), subsequent study will be focused on more complex geometry and realistic physics to acquire a comprehensive and exhaustive view of the problem.

With the large-scale use of intermittent renewable energy worldwide, such as wind energy and solar energy, energy storage systems are urgently needed and have been rapidly developed. Technologies o ...

The present work aims to provide a comprehensive early-stage approach to optimise the design, synthesis and operation of a marine energy system for liquified gas carriers, considering their economic and technical aspects, and also weather along the route. Part A of this work details the approach that we have developed while Part B will summarise the first part, it will then describe the case study, results and discussion, as well as the conclusion. Various propellers, 16 engines and 4 operational profiles are assessed. In this part, we will apply a differential evolution optimisation algorithm, whose objective function will be maximised as the net present value. The case study is designed to use a liquefied natural gas carrier of 175,000 m3 sailing between Lake Charles (USA) and Tokyo Bay (Japan), via the Panama Canal. All of the suitable matchings for 15,023 propellers are found. This approach shows a gain of 22% between the worst individual of the initial population and the worst individual of the final population. The required brake power is approximately 22% higher for rough weather than for still water. A difference of over 120% was found by comparing varied matchings of economic scenarios and fuel profiles. Our approach shows a significant gain and highlights the value of exploring a broad range of energy system configurations in an integrated manner, especially considering the weather conditions.

Systematic field measurements were carried out at the sliding area of the Xingfeng Landfill, which is a large high food waste content municipal solid waste (HFWC-MSW) landfill. Sixteen boreholes were drilled and pore pressure transducers, gas pressure pipes and inclinometer pipes were installed to measure pore water pressures, pore gas pressures and waste displacements, respectively. Two measuring lines of electrical resistivity tomography (ERT) were arranged to analyze the liquid-gas distribution in the waste mass. In addition, a stability analysis was conducted on the basis of the measured results. The main findings are as follows: (i) In the regions at the depths of 5–15 m in the waste mass, the saturation level of the waste was relatively high, and high gas pressures were not evident. However, in the regions at depths blow 15–20 m, the waste was unsaturated, and there were obvious local high gas pressures, (ii) The low-water-content and high-water-content zones obtained by ERT corresponded to the low-saturation and high-saturation zones inferred by the measurements of the water and gas pressures, respectively, indicating the consistency between the results of ERT and drilling, and (iii) By field measurement and stability analysis, the correlation between high gas pressures and sliding was confirmed, indicating high gas pressures may be the critical cause for the frequent waste sliding. In addition, the possible causes for the liquid-gas distribution and high gas pressures in the waste mass were discussed by considering the biodegradation characteristics of HFWC-MSW. This study provides the references for field measurement and stability control in similar landfills.

Migration of gas and oil production facilities to remote northern regions of the country, increase in the unit capacity of the equipment set the task of increasing the service life and reliability of equipment for the extraction and transportation of gaseous and liquid media. One of the main reasons for the accelerated failure of equipment is the corrosion effect of transported media. In this work, the effect of corrosion under stress on the performance of the main metal and welded joints of stainless pipes of austenitic-grade chromium-nickel steels has been studied. It is shown that the rate of the anodic process increases as the level of plastic deformation increases and the rate of growth depends on the degree of imperfection of the structure of the material. It has been established that the heat-affected zones of assembly welded joints of austenitic steels are the most prone to corrosion cracking, and the requirements for restoring the structure of heat treatment of the weld are not fulfilled. Refusal of heat treatment leads to the appearance and growth of carbide particles in the structure of the heat-affected zone, which reduces almost by a factor of two, from 270 to 150 MPa, the level of stresses, leading to the occurrence of corrosion cracking in welded joints.

We explore the relationship between freight rates of Liquified Natural Gas (LNG) and Liquified Petroleum Gas (LPG) carrier freight rates, and the global geopolitical risk, while also controlling for the macro environment. Our results show that a shock in geopolitical risk significantly increases the cost of the spot charter rates for both the LNG and LPG carriers, with the impact reaching around 25% for the former and 18% for the latter. Our results bare significant implications for the companies and countries involved in the liquefied gas trade, as it is likely to continue substituting other fossil fuels in the future. As such, the significance of a stable energy source makes it highly correlated with the economic development and energy security in the importing countries.

New electrocatalysts with high reduction efficiency are needed to upgrade the mediated electrochemical reduction for real applications. In addition, automation is required to quantify active electrocatalysts in alkaline media and air pollution. In this study, N2O was removed sustainably by electrogenerated low valent nickel(I) phthalocyanine tetrasulfonate [Ni(I)TSPc] in 1 M KOH using an electroscrubbing system. Ni(I)TSPc electro generation and N2O removal were automated by two (liquid/gas) electrochemical flow sensors, respectively. The Ni(I)TSPc was generated electrochemically up to 95% in 1 M KOH, and high removal efficiency (100%) was observed for 5 ppm N2O and 90% for 10 ppm N2O. A limiting potential change in the in-situ LSV of the chemically synthesized Ni(I)TSPc was taken and derived from the calibration plot and validated by an ex-situ potentiometric titration using an oxygen reduction potential electrode. Using the obtained calibration plot, electrogenerated Ni(I)TSPc allowed a direct determination in a liquid flow cell. The gas flow sensor developed using a KOH/Ni(II)CN4 (TCN (II))-fabricated silver solid amalgam electrode showed an excellent response to N2O concentrations up to 32 ppm. A calibration plot with known concentration was derived and validated by gas chromatography. The response time and sensitivity obtained were approximately 500s and −0.012 mA ppm−1 cm−2, respectively. The sensor stability test confirmed its good stability. Finally, the developed in-situ electrochemical flow sensors were applied to the sustainable automation of N2O pollutant removal.

The frequent occurrence of Liquefied natural gas (LNG) leakage accidents has caused serious economic loss and environmental damage. Therefore, it's of great significance to make assessments on the LNG hazards during its accidental release and associated consequences. This paper focuses on the two-phase release process in the liquefied gas release and dispersion accident and makes investigatatation on the two-phase plume with experimental and numerical approaches. A small-scale experimental system is developed with different sizes of release holes. With the experiment results, the mass outflow rate and temperature have been obtained, which provided initial parameters for the simulation. Jet velocities have been measured by PIV, and results reveal that an obvious velocity breach existing near the leakage nozzle due to the Joule-Thomson effect. Besides, given a point in the X-axis, the jet velocity is decreasing with an increasing diameter hole. Subsequently, the experimental data are utilized to verify the liquid-gas phase numerical model using Eulerian-Lagrange approach. Comparing with the results obtained by single gas phase model, the velocities obtained by liquid-gas phase model show good consistency with the experiments. Afterwards, the validated numerical liquid-gas phase model is employed to analyze the temperature distribution, concentration distribution and droplet size distribution in the near-source release region. With the simulation results, it depicts that there is a violent temperature decrease near the leakage nozzle in the liquid-gas phase model, which was caused by the evaporation of droplets. Meanwhile, concentration of R134a simulated by liquid-gas phase model is higher than the value of single-gas phase. These results emphasize that it’s essential to simulate the release accidents with liquid-gas phase model, especially in the near-source region. Both the experiments and numerical models are of great value for providing assessments and theoretical supports for the risk consequences in the process safety.

The multiphase flow occurs in various major industrial fields and nature. Furthermore, due to the single and multiphase flow characteristics, they generate vibration on the structure conveying or subjected to the flow. This paper investigates in an experimental apparatus, the possibility to use the flow-induced vibration from a vertical liquid-gas two-phase flow conveyed by a pipe to obtain the elongated bubble velocity. The vibration signal analysis in time domain showed that the structural excitation due to the elongated bubble rising in the stagnant liquid was significant to be distinguished from other excitations. The time-frequency analysis of slug and churn flow showed a significant amplitude variation in a specific frequency band. Finally, it was possible to obtain the elongated bubble velocity with reasonable accuracy by cross-correlating the envelope of a vibration signal filtered in a particular frequency band of two accelerometers. Thus, this paper presents a non-invasive and simple to mount technique to estimate the elongated bubble velocity in stagnant and moving liquid conditions.

Standard practice for determining permeability is to perform gas permeability measurement and apply correlations to receive corrected permeability as the value of absolute permeability . However, these correlation are dedicated for the specific reservoirs or unconsolidated porous media and cannot be applicable for other rock formations. The objective of this study is to establish correlation between liquid and gas permeability for the pure dolomite . A series of liquid and gas permeability measurements were performed on cylindrical rock samples from formation located in Poland. To determine Klinkenberg-corrected gas permeability, measurements of gas permeability at three (randomly selected) different inverse mean pressure were extrapolated to infinity . Then values of water and corrected-gas permeability were contrasted against each other. The results showed that Klinkenberg permeability overestimates water permeability and the observed difference is in range of 11–24%. This fact can be caused by water polar nature. Hydrogen bonds are formed with neighboring molecules and cause high surface tension and capillary forces . Later, the effect of overburden pressure on water permeability was studied and results showed reduction in permeability as a function of increasing stress. In the last part of the research, the permeability values obtained by using novel equation has been compared with values using other mathematical formulas designed for sandstone and limestone. We learned that our correlation provides results with higher accuracy than the previous equations.

High-entropy alloys have shown exceptional damage tolerance at cryogenic temperatures. Here we report that this essential property can be maintained even when exposing the equiatomic CoCrFeMnNi alloy to the most detrimental environmental condition known to metals, hydrogen. This is enabled by a self-accommodation mechanism: the higher the local hydrogen content, the higher the twin formation rate as hydrogen reduces the stacking fault energy. Thus, the hydrogen’s through thickness diffusion gradient translates into a nano-twin gradient that counteracts material weakening by enhanced local strengthening. The concept targets applications under harsh and cryogenic conditions, such as encountered in arctic, offshore, energy and liquid gas chemical processing, and transport operations. The new mechanism opens a pathway to the design of alloys that withstand heavy mechanical loading under cryogenic and hydrogen-containing conditions.

Indoor go-karting is a popular free time activity for many people, including adults and children. Particulate matter from engine emissions, brake and tire debris and gaseous pollutants are important sources of air pollution. Exposure to these air pollutants is associated with health-related problems. In this study, the exposure of employees and spectators to particulate matter was measured in 8 indoor go-kart facilities (6 facilities used gasoline, one used liquid gas and one used electricity for their go-karts). The mass concentrations of particulate matter were continuously analyzed. Particles were sampled and analyzed by inductively coupled plasma mass spectrometry and electron microscopy coupled with energy-dispersive X-ray spectroscopy. The mean PM10 concentrations ranged between 4.9 and 34.9 μg/m³ for workplaces and 5.6 and 28.4 μg/m³ for spectator areas. The mean PM2.5 concentrations measured in workplaces ranged from 2.3 to 29.2 μg/m³ and from 2.4 to 27.4 μg/m³ in the spectator areas. The highest PM10 and PM2.5 concentrations were measured at the liquid gas go-kart facility and at go-kart facilities with the maximum number of go-karts running simultaneously. The electric go-kart facility showed high PM10 concentrations but low PM2.5 values. The highest particle number concentration was measured in the workplace of the facility using liquid gas go-karts (2.7 × 105 particles/cm³), and the lowest concentration at both measurement points of the electrical go-kart facility (1.8 × 104 particles/cm³). Metals such as copper, zinc, strontium, barium, aluminum, calcium, manganese, iron and nickel were found in nearly all samples with help of inductively coupled plasma mass spectrometry. The most abundant metal was iron, with concentrations up to 5.6 μg/m3 (electric go-kart facility). Electron microscopic investigations showed high concentrations of soot in all samples, except for the samples of the electric go-kart facility. Additionally, agglomerates with iron and other metals were found in all samples. To summarize, electric go-karts, combined with a good ventilation system, seem to be more suitable for indoor use.

Cold-stretching is an important lightweight technology for reducing cost of cryogenic vessels, which are widely used for storing liquefied gas. This paper studied the influence of cold-stretching on the buckling behavior of cylindrical vessels with different initial out-of-roundness under external pressure. Buckling pressures, strains, and buckling modes of cylindrical vessels were obtained from experiments. A 3D laser scanner was used to obtain the complicated geometry of the vessels before and after cold-stretching. Based on the 3D scanned geometry, we performed FEA to evaluate the buckling pressures, which resulted in a good agreement with the experimental values. The effects of cold-stretching on buckling are discussed based on four factors: out-of-roundness, thickness, diameter and yield strength. Firstly, buckling of cylindrical vessels is elastic buckling in our case, so yield strength has no influence on buckling pressure. Secondly, the negative effect of diameter-thickness ratio increasing was proved to be slight (within 3.3%) in our case. Finally, buckling pressure increased after cold-stretching because out-of-roundness decreased. Experiments showed that buckling pressures were enhanced by 10.8% and 13.6% after cold-stretching for long and short cylindrical vessels with 1.9% and 1.6% in out-of-roundness.

This study evaluates the structural feasibility of a prismatic pressure vessel using strength assessments. A prismatic pressure vessel, which differs from a cylindrical or spherical pressure vessel, is proposed. A prismatic pressure vessel can be used to ship liquefied gas. A prototype of the prismatic pressure vessel was designed, manufactured and tested in accordance with the ASME Boiler and Pressure Vessel Code. Its design uses the “design-by-analysis” method, including protection against plastic collapse. The prototype of the prismatic pressure vessel uses typical construction materials considering their linear elastic and nonlinear plastic behaviors. The vulnerable components of the structure were obtained through numerical analysis using the finite element method. A pressure test with strain gauges was conducted, and the results demonstrate the feasibility of the prismatic pressure vessel as a suitable vessel for high-pressure fluids with high volume efficiencies. The prismatic pressure vessel has potential for general applicability in the shipping of liquefied gas.

This paper presents the results of an investigation into the failure of steam boiler tubes in a liquefied gas treatment plant. The failure appeared in the form of a window rupture in the boiler tubes of 1.25Cr-0.5 Mo grade steel. Study revealed that a thick magnetite iron oxide layer was formed in the inner surface of these tubes, disturbing the heat flow and rising the temperature of the tubes. Consequently, the internal oxide layer led to a series of metallurgical degradation and the loss in mechanical strength of the boiler tubes. Failure analysis of the steam tubes was carried out by optical and scanning electron microscopy examinations, chemical analysis of the tube material and the results showed that the scales were formed in the inner surface of the tubes. Furthermore, the rise in operational temperature and its distribution were simulated using fluent software and the results were compared against the designed temperature of the tubes. The simulation revealed that the operating temperature of the tubes reached beyond the design temperature, confirming the microstructural degradations i.e., oxidation, decarburization and reduction in the effective tube wall thickness. The extensive scale formation on the steam side and the resultant tube wall thinning was identified as the main cause of failure in the superheater tubes.

This study investigates the multiphase flow of a liquid-gas-particle mixture in dam break. The open source codes, OpenFOAM and CFDEMproject, were used to reproduce the multiphase flow. The results of the present study are compared with those of previous results obtained by numerical and experimental methods, which guarantees validity of present numerical method to handle the multiphase flow. The particle density ranging from 1100 to 2500 kg/m3 is considered to investigate the effect of the particle density on the behavior of the free-surface and the particles. The particle density has no effect on the liquid front, but it makes the particle front move with different velocity. The time when the liquid front reach at the opposite wall is independent of particle density. However, such time for particle front decrease as particle density increases, which turned out to be proportional to particle density. Based on these results, we classified characteristics of the movement by the front positions of the liquid and the particles. Eventually, the response of the free-surface and particles to particle density is identified by three motion regimes of the advancing, overlapping and delaying motions.

The surface tension of chemical compounds controls some of the important processes in chemical engineering. On the other hand, surface tension is recognized as one of the most difficult thermo-physical properties to correlate or predict. In this paper, it was shown how to use a novel combination of the group contribution method and a mathematical-based algorithm to develop a predictive model. In this study, Gene Expression Programming (GEP) was used and the performance of the model developed was measured. Additionally, a comparison study was performed between newly developed corresponding states model and the previously published correlations available in the literature. Accordingly, it was demonstrated that there was a good agreement between predictions using the model proposed and the literature-reported data for surface tension. The results indicated that the model proposed was more reliable than the available correlations for determination of the surface tension of liquid gases, from an error analysis point of view.

Emission models are useful tools for the study and management of atmospheric emissions from passive liquid surfaces in wastewater treatment plants (WWTPs), which are potential sources of odour nuisance and other environmental impacts. In this work, different theoretical and empirical models for the gas-side ( k G ) and liquid-side ( k L ) mass transfer coefficients in passive surfaces in WWTPs were critically reviewed and evaluated against experimental data. Wind forcing and the development of the wind-wave field, especially the occurrence of microscale wave breaking, were identified as the most important physical factors affecting mass transfer in these situations. Two approaches performed well in describing the available data for k G for water vapour. One is an empirical correlation whilst the other consists of theoretical models based on the description of the inner part of the turbulent boundary layer over a smooth flat plate. We also fit to the experimental data set a new, alternate equation for k G , whose performance was comparable to existing ones. However, these three approaches do not agree with each other in the whole range of Schmidt numbers typical for compounds found in emissions from WWTPs. As to k L , no model was able to satisfactorily explain the behaviour and the scatter observed in the whole experimental data set. Excluding two suspected biased sources, the WATER9 (US EPA, 1994. Air Emission Models for Waste and Wastewater. North Carolina, USA. EPA-453/R-94–080A) approach produced the best results among the most commonly used k L models, although still with considerably high relative errors. For this same sub-set, we propose a new, alternate approach for estimating k L , which resulted in improved performance, particularly for longer fetches. Two main gaps were found in the literature, the understanding of the evolution of the mass transfer boundary layer over liquid surfaces, and the behaviour of k L for larger fetches, especially in the range from 40 to 60 m.

This study explored flow patterns and void fraction prediction models for co-current upward liquid-gas two-phase flow in narrow annular spaces. Experiments on two-phase flow in both narrow and wide annular conduits were performed in a 4-inch (0.102 m) outside-diameter test section, with 3.5-inch (0.089 m) and 2-inch (0.051 m) inner pipes as representations of different annular geometries. Flow patterns and liquid holdup were recorded while flowing air and water upward through the test sections. The experimental results showed that the two-phase flow pattern maps in narrow annulus and wide annulus are with different major regime transition lines. A new drift-flux model for water-air two-phase flow in narrow annuli was developed using experimental data collected in this study. The new model was compared against previous models that were developed for wide annuli, and the results showed a better match in void fraction predictions for two-phase flow in narrow annuli with experimental data. The understanding of two-phase flow in narrow annuli is vital for real-time prediction of void fraction and annular pressure loss in wells with gas influx during casing/liner/slimhole drilling operations. An enhanced prediction can ensure delivery of safer wells with lower non-productive time and associated trouble encountered during well control operations.

The non-invasive technique is one of the favourite methods applied in process plants, compared to other sensing techniques. Due to certain advantages, this technique is also implemented in process tomography such as in non-invasive ERT systems for multiphase mixtures. The purpose of this paper is to investigate the optimum size of the area of the electrode in terms of the width and height for the non-invasive ERT system that can be applied for a static liquid-gas regime. Based on a quasi-static electric field, a 2D simulation using finite element model software (COMSOL Multiphysics) was used to analyse the simulation results. As a result, by applying several widths and heights to the system, 18.5° and 200 mm in width and height, respectively, were chosen as the optimum dimensions to be applied for a 100 mm outer diameter and 2 mm thick acrylic pipe for the non-invasive ERT electrode. Later, experiments were conducted to obtain the tomogram for image verification. Thus, it is believed that the implementation of the optimised area of the electrode can allow the electricity to be emitted and significantly detected. The non-invasive ERT system will also give an alternative way for industry to monitor the performance of process plants.

This paper attempts to propose an optical fiber sensing system based on the vortex beam, which can be applied to measure liquid refractive index (RI), gas concentration and displacement. Its sensing structure consists of a silver-coated microfiber for surface plasma resonance (SPR) sensors, a fiber aligned with it, and a interference structure for Gaussian beam interfering with the transmitted vortex beam. Due to SPR effect, when the RI of liquid changes, the wavelength of resonance spectrum will shift accordingly, thus the sensitivity of the RI can be achieved. When the gas refractive index n and distance L between two fiber end face change, phase difference will be generated between the transmitted vortex beam and the bypass Gaussian beam. Thereupon, the interference pattern of the two beams will rotate, the measurement of the gas RI and displacement can be achieved. In comparison with the traditional optical fiber SPR sensor, the simulation result shows that SPR excited by the vortex beam is more explicit with higher sensitivity. When the RI of the external environment is 1.385, the sensitivity of 4600 nm/RIU under the condition of Gaussian beam, the sensitivity of sensor based on vortex beam increases to 6800 nm/RIU, which is 47.8% higher. When the RI of the external environment is 1.365–1.385, the average sensitivity of the sensor increases from 3950 nm/RIU to 5100 nm/RIU. Meanwhile, the gas RI sensitivity is 36°/0.0001 RIU and the displacement sensitivity is 36°/ 100 nm. In terms of the CCD angle resolution, the theoretical resolution of gas RI measurement is 1.54e-10 RIU, and the resolution of displacement is 1.54e-4 nm.

Direct coal liquefaction residue (DCLR) was blended with five bituminous coals to prepare crucible coke in the laboratory. A new index liquid-gas ratio (LGR) was defined to quantify relative amounts of liquid phase and gas phase during coking. Great attention was paid to the early stage of coking (400−600 ℃) and then LGR was modified to LGR(t). Relationships and mechanism between LGR, LGR(t) and coke strength were investigated and summarized. Results showed that when high caking property coal ratios was inadequate ( 60 %) and the content of gas druing coking matched the content of metaplast (rational LGR and LGR(t)).

Consumers are daily exposed to a range of mineral oil hydrocarbons via food consumption. Major sources of MOH in food are packaging and additives, processing aids, and lubricants. In 2019, an EU guidance was released covering specific directions for sampling and analysis of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) in food and food contact materials within the frame of Recommendation (EU) 2017/84 for the monitoring of mineral oils. The parameters required by the guide are increasingly stringent, and coping with this type of analysis is now very challenging. It is within such a context that the present research is confined, inasmuch that it is focused on the construction of a low-cost, lab-made Y-interface for liquid-gas chromatography coupling used for the determination of MOSH and MOAH in foodstuffs. The response ratios of alkanes comprised between C10 and C50 were measured and were comprised between 0.9 and 1.1, with a maximum coefficient of variation of 4% (n = 5). Intermediate precision was evaluated for the fat/oil category during a period of 48 days obtaining a value of 10%. Qualitative and quantitative analysis of both MOSH and MOAH were performed in a single run and in a fully-automated manner. Seventeen different foods were analyzed in order to cover the categories reported in the EU guide. Saturated hydrocarbon contamination was detected only in a few samples (in the range 1–153 ppm); MOAH contamination was found only in one sample (sunflower oil: 15 ppm).

On June 5, 2017, there was a Vapor Cloud Explosion (VCE) at JinYu Petrochemical Co. Ltd. During unloading of liquified natural gas, the gas leaked from the truck and formed a vapor cloud, then the vapor cloud met with the electrical sparks in the plant laboratory, and an explosion occurred. This incident caused significant casualties and property loss. The main causes of the accident are demonstrated by a fishbone diagram. The major causes include (a) defective design, (b) noncompliance with standard operation procedures (SOPs), (c) the presence of ignition sources, (d) ineffective enforcement of safety rules, (e) inadequate design of emergency facilities, and (f) delayed emergency response. The analysis reveals that process safety management (PSM) is a crucial factor in the success of chemical plants, especially for small and median-scale companies in developing countries. Dispersion phenomenon of liquefied gas is simulated by commercial Computational Fluid Dynamic (CFD) software. The simulation results approximately agree with the real incident. The simulation indicates that a visual and quantitative consequence analysis can provide general guidance for PSM. Finally, based on various PSM conditions (good, normal, weak, and bad), the probabilities of VCE generated from leakage are obtained by an event sequence diagram (ESD) and Monte Carlo methodology. By comparing the quantitative probability values in four different PSM situations, the results show that emergency management associated with effective PSM is crucial to avoid VCE incidents.

The novel titanium thin/tunable liquid/gas diffusion layers (TT-LGDLs) with precisely controllable pore morphologies have achieved superior multifunctional performance in proton exchange membrane electrolyzer cells (PEMECs) with its advantages of ultra-thin thickness (25 μm), planar surface, and straight-through pores. By taking advantage of the precise pore morphology of TT-LGDLs, a comprehensive computational model is developed in MATLAB/Simulink platform to simulate the CL current distribution, and PEMEC electrochemical performance. The interfacial contact resistances between the TT-LGDLs and catalyst layers (CLs), and PEMEC overpotentials are closely correlated to the TT-LGDL pore diameter and porosity. In addition, the roughness factor, which is a critical coefficient in simulating the activation overpotential in Butler-Volmer equation, is also modeled as a function of TT-LGDL morphologies. More importantly, a novel two-dimensional (2D) CL resistance model that consists of both in-plane and through-plane resistances is also developed to predict the current distribution on the CLs. The present model can precisely match the experimental results and effectively calculate the PEMEC performance with different TT-LGDL morphologies and operating temperatures. Results obtained from the present model will provide a deep understanding of the functions of TT-LGDL morphology, and also help to optimize the design and fabrication of both the TT-LGDLs and CLs.

Accepted: 2017-07-31, 資料番号: SA1170123000

The boiling liquid expanding vapor explosion (BLEVE) is a most common hazard in liquefied gas storage and transportation. The explosion is resulted from tank overpressure under external thermal attack, and its prevention depends on accurate prediction of the boiling liquid pressurization. This paper presents a mathematical model to simulate the boiling liquid pressurization in liquefied gas storage tank. The model includes a semi-empirical equation to calculate the critical subcooled degree at the onset of pressurization, an energy equation of bubble condensation to calculate the net vapor generation rate in storage tank, a thermal-response equation of the subcooled boiling liquid to calculate the transient temperature of bulk liquid, and an isochoric equation to predict the transient pressure of boiloff liquefied gas. Comparison of the model predictions with experimental data shows that the maximum deviations of the predicted transient pressure and temperature are within 15 kPa and 3 °C, respectively.

The high food waste content (HFWC) MSW at a landfill has the characteristics of rapid hydrolysis process, large leachate production rate and fast gas generation. The liquid-gas interactions at HFWC-MSW landfills are prominent and complex, and still remain significant challenges. This paper focuses on the liquid-gas interactions of HFWC-MSW observed from a large-scale bioreactor landfill experiment (5m×5m×7.5m). Based on the connected and quantitative analyses on the experimental observations, the following findings were obtained: (1) The high leachate level observed at Chinese landfills was attributed to the combined contribution from the great quantity of self-released leachate, waste compression and gas entrapped underwater. The contribution from gas entrapped underwater was estimated to be 21-28% of the total leachate level. (2) The gas entrapped underwater resulted in a reduction of hydraulic conductivity, decreasing by one order with an increase in gas content from 13% to 21%. (3) The "breakthrough value" in the gas accumulation zone was up to 11kPa greater than the pore liquid pressure. The increase of the breakthrough value was associated with the decrease of void porosity induced by surcharge loading. (4) The self-released leachate from HFWC-MSW was estimated to contribute to over 30% of the leachate production at landfills in Southern China. The drainage of leachate with a high organic loading in the rapid hydrolysis stage would lead to a loss of landfill gas (LFG) potential of 13%. Based on the above findings, an improved method considering the quantity of self-released leachate was proposed for the prediction of leachate production at HFWC-MSW landfills. In addition, a three-dimensional drainage system was proposed to drawdown the high leachate level and hence to improve the slope stability of a landfill, reduce the hydraulic head on a bottom liner and increase the collection efficiency for LFG.

It has been reported that the phenomena of explosive boiling always occur during the storage and transport of the liquefied gases such as hydrogen. The accident usually followed the rapid depressurization of the liquefied gas storage tanks, which was caused by the rupture of the tank or the opening of the safety valve, and could bring secondary hazards by the pressure re-built. The explosive boiling process involved a complicated coupling between the response of the pressure and the boiling of the liquefied gases. In this paper, a mathematical model was developed to predict the coupled response between the pressure and the unstable boiling of the liquefied gases. And good agreement was obtained between the experimental data and the simulated results of the pressure response. The mechanism of the coupled response between the pressure and the superheated liquid boiling, as well as the evolution of the two phase flow during the discharge were researched by analyzing the pressure transmission process, the vaporization rate contribution and the hydrodynamic field.

It is a common situation that the liquefied gas tanks are always heated by the outer hot environments, which affecting the safety of the tanks. In this paper, numerical studies were conducted to reveal the heat transfer characteristics of this circumstance. The coupled heat transfer process among the thermal environment, the tank wall and the fluid in the tank was thoroughly investigated by simultaneously solving the temperature fields of both the solid region and the fluid region as well as the flow fields of both the liquid phase and the vapor phase inner the tank. The results showed that affected by the near wall flow and the wall boiling, the heat transfer presented different patterns in the stable thermal stratification stage and the de-stratification stage. In the stable stratification stage, the heat flux from the liquid phase wall to the medium distributed uniformly along the axial direction of the tank, while in the de-stratification stage, it differed a lot at the different positions.

An iterative procedure for optimizing the NH3-based carbon capture process was designed. Based on the rate-based model, process optimization of CO2 capture by aqueous ammonia was performed. The object of this process is one million tonnes of CO2 captured annually at a capture efficiency of 90%. Thus, 31.45% of the total flue gas from a typical 500 MW coal-fired power plant was drawn into this CO2 capture system. Three parameters, namely α (the ratio of the CO2 absorption rate to the mass flow rate of the lean solvent), β (the ratio of the CO2 absorption rate to the packed volume of the absorber), and γ (the ratio of the CO2 output to the packed volume of the stripper) were defined for considering the operating and construction costs. Effects of liquid gas ratio, boilup ratio, and column sizes on this process were investigated, and these parameters were optimized. The optimal condition can achieve the object of this process, and its low regeneration energy shows a good prospect of CO2 capture by aqueous ammonia.

In the vicinity of critical point neither the nominal liquid nor the nominal gas is a single, homogeneous phase. This is a consequence of the presence of heterophase fluctuations. Theoretical models accounting for such fluctuations are necessary to estimate their role and importance at the gas-liquid criticality. Two mesoscopic models of the heterophase fluid are formulated here to solve this problem. The first one is a mean-field mesoscopic lattice model of fluid in which the lattice cells are occupied by “bubbles” and “droplets” called liquid-like and gas-like fluctuons respectively. In this model an order parameter is introduced to characterize the two-state mesoscopic structure. Its relation to the Van der Waals order parameter is found, an equation of state is deduced, and the phase coexistence curve is determined. The Yang-Yang anomaly amplitude and the amplitudes of the leading singular terms of the diameter of the density-temperature coexistence curve (density diameter) are determined in terms of the mesoscopic parameters of asymmetry. In the second model, which generalizes the first one, the fluctuons have no fixed shape and volume. Criticality of the irregular array of fluctuons is then studied.

International audience; An analytical procedure comprises two steps: sample preparation mostly extraction (Soxhlet, Dean–Stark, Likens– Nickerson, Blye & Dyer, Folch, leaching, maceration, percolation) and analysis (spectrophotometry, chromatography, spectrometry). Whereas chemical analysis is finished after few minutes, extraction takes at least several hours and requires large solvent volumes, energy-consuming for concentration step by evaporation to recover the final extract. In this current opinion we provide an instantaneous picture of current knowledge on alternative and green solvents used in analytical laboratories for sample preparation and extraction of natural product in terms of innovation, original procedures, and safe products. We discussed how bio-based solvents, water in different forms, deep eutectic solvents, liquefied gas have already become an important issue in the sample preparation in analytical chemistry of natural products replacing petroleum and hazardous solvents.

CO2 carriers are considered as a solution for CO2 transport as a part of Carbon Capture and Storage. CO2 carriers' design is similar to that of commercial liquefied gas carriers and core technology of liquefied gas carriers is to handle boil-off gas during voyages. This paper introduced newly developed CO2 boil-off gas re-liquefaction processes making use of cold LNG fuel and investigated economic feasibility of newly developed processes by comparison with a conventional boil-off gas re-liquefaction process. New processes enabled considerable main equipment costs saving and additional fuel cost saving for re-liquefying boil-off gas. Simulation study results showed total amount of boil-off gas in a LNG fueled CO2 carrier could be re-liquefied by LNG fuel consumed during the voyage and comparative cost assessment results demonstrated those newly developed processes could be applied into a LNG fueled CO2 carrier with insignificant additional cost. The finding of this paper confirms those newly introduced processes are technically and commercially feasible at present and will contribute to growing the potential market of LNG as a marine fuel as well as commercializing CCS technology by providing more cost-effective solution for CO2 shipping.

The kinetics of spontaneous liquid-gas imbibition in micropores of carbon molecular sieves (CMSs) used for air separation has been investigated. Based on the kinetics, the microporous textures of CMSs could be estimated, and a new assessment method for O2/N2 separation performance of CMSs in pressure swing adsorption (PSA) was established. Water was chosen as the imbibition liquid probe, and N2 and O2 were chosen as the gas probes. The pseudo-second-order (PSO) kinetic model and the linear driving force (LDF) model were employed to confirm that the rate-limiting steps of the spontaneous water-O2/N2 imbibition were mainly attributable to the surface adsorption of water and the diffusion of gas through the micropore entrence or interior in CMSs. Water molecules invade into the narrower micropore mouths prior to the wider micropore mouths. An O2/N2 selectivity coefficient K was established to assess the air separation performance of CMSs. When the K value is equal to zero, the size distribution of micropore mouths in CMSs is the fittest for the air separation and the highest N2 production can be obtained. But with K gradually deviating zero, the air separation performance of CMSs decreases.

Efficient storage of hydrogen is crucial for the success of hydrogen energy markets (early markets as well as transportation market). Hydrogen can be stored either as a compressed gas, a refrigerated liquefied gas, a cryo-compressed gas or in hydrides. This paper gives an overview of hydrogen storage technologies and details the specific issues and constraints related to the materials behaviour in hydrogen and conditions representative of hydrogen energy uses. It is indeed essential for the development of applications requiring long-term performance to have good understanding of long-term behaviour of the materials of the storage device and its components under operational loads.

We present experimental and numerical lifetime investigations of evaporating water drops on solid surfaces depending on the shape and size of their liquid/gas interface. The simulations are based on an Allen–Cahn type phase-field model, where the liquid–gas phase transition is driven by a concentration gradient. The experiments are conducted under defined initial and constant conditions. Throughout the whole experiment, contact angle, temperature, relative air humidity and drop weight are tracked continuously. The numerical and experimental results are compared with analytical predictions. In our study, we confirm that the lifetime of a drop is directly linked to its surface size and shape. We compare lifetimes of evaporating drops on smooth solid surfaces with different contact angles and find an increase in lifetime by 50% as the contact angle increases from 20° to 90°, both in experiments and in simulations. Furthermore, drops placed in different geometric set-ups such as a wedge or a corner show a lifetime behavior that is in accordance with analytical predictions. The presented computational approach captures experimentally measured drop lifetimes, for various set-ups, very well. These findings are especially relevant for industrial questions such as how fast complex components dry after cleaning or how long it takes till lacquer layers are cured on structured surfaces.

Slug flows are commonly found in oil and gas offshore production operations, where pressure drop estimation is essential for facilities design. Several studies have been made to evaluate pressure drop for slug flows in smooth pipes. However, many offshore oil production lines consist of corrugated pipes, and the drag induced by the discrete cavities is rarely investigated for slug flows. For this purpose, an experimental flowloop was designed to measure pressure drop of air-water slug flows in 26 mm-ID corrugated pipes with four different groove geometries, consistent with the groove configurations used in offshore petroleum exploitation. The experimental data is regressed using the concept of pressure drop multipliers. Whilst this procedure is well established in literature for smooth pipes, an additional multiplier associated to the effect of the corrugated pipe on the pressure drop is proposed in this work. With such approach, a correlation for the pressure drop in horizontal liquid-gas slug flows in corrugated pipes is obtained by means of the groove geometry and the flow input data. Comparison of the proposed model predictions with experimental data shows ±7% accuracy.